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Sound
1. Sound
Sound is a form of energy that produces the sensation of hearing. It is produced due to the vibration of objects. Example: Sound is produced when a guitar string is plucked or a bell is struck.
2. Production of Sound
Sound is produced when an object vibrates. These vibrations make the surrounding air particles vibrate, and sound travels through the medium.
3. Sound Needs a Medium
Sound cannot travel in vacuum. It requires a material medium such as: solid liquid gas
4. Sound as a Longitudinal Wave
Sound travels in the form of longitudinal waves consisting of: compressions (high pressure regions) rarefactions (low pressure regions)
5. Characteristics of Sound
(a) Amplitude
The maximum displacement of vibrating particles from their mean position. It determines the loudness of sound.
(b) Time Period (T)
The time taken to complete one vibration. Unit: second (s)
(c) Frequency (f)
The number of vibrations per second. Unit: hertz (Hz) Frequency determines the pitch of sound.
(d) Loudness
Loudness depends on the amplitude of the sound wave. Unit: decibel (dB)
(e) Pitch
megaphones horns soundboards in auditoriums stethoscope
11. Range of Hearing
Human hearing range: 20 Hz to 20,000 Hz Below 20 Hz → infrasonic sound Above 20,000 Hz → ultrasonic sound
12. Ultrasound
Ultrasound is sound with frequency greater than 20,000 Hz. Uses of ultrasound: medical imaging (sonography) detecting cracks in metals cleaning delicate instruments
13. Important Points
Sound is produced by vibrating objects It cannot travel in vacuum Frequency determines pitch Amplitude determines loudness Speed of sound depends on medium Human ear range is 20 Hz to 20,000 Hz Echo is due to reflection of sound
